1. Field of the Invention
The present invention relates to a light-emitting semiconductor device (LED) or an optical semiconductor device including a light detection device and so on which has at least one p-n junction structure. Especially, the invention relates to an optical semiconductor device which has a highly resistive region to control the flow of current.
2. Description of the Related Art
Conventionally, an electrode of an optical semiconductor device, especially a nitrogen compound LED having at least one of gallium (Ga), aluminum (Al), and indium (In) therein, is formed at a corner of the semiconductor chip so as not to effectively interfere with light produced by the device. The electrode is formed using bonding processes.
However, an opaque electrode pad is formed on some part or area of the electrode so that emission light from an area below the electrode pad is unable to contribute to luminous intensity of the device. The electric current which contributes to such blocked light is thus not used effectively.
Such unnecessary current flow causes the LED to age, because the region below the electrode pad is expected to be mechanically damaged at the time of wire bonding and the unnecessary current flow through that region increases the deterioration of the LED. As a result, the life span of the LED is limited, making the LED an unreliable product.
It is, therefore, an object of the present invention to improve the efficiency of applied current to an LED.
It is another object of the present invention to improve the quality of the LED.
According to a first aspect of the invention, an optical semiconductor device is provided having a p-n junction structure made of an n-layer and a p-layer, an electrode pad for wire bonding and a highly resistive region below the electrode pad.
According to a second aspect of the invention, the highly resistive region is made of silicon oxide (SiO2).
According to a third aspect of the invention, the highly resistive region is formed as some part of or an area of the p-layer, before the p-layer is processed to exhibit p-type conduction.
According to a fourth aspect of the invention, the highly resistive region is formed by annealing over the electrode pad after the electrode pad is formed.
According to a fifth aspect of the invention, the highly resistive region is formed by ion implantation and/or impact which diffuses insulators into some part or area of the p-layer.
According to a sixth aspect of the invention, the optical semiconductor device comprises a nitride compound semiconductor LED having at least one of aluminum (Al), gallium (Ga) and indium (In).
The highly resistive region or insulative region formed below the electrode pad redirects the applied current from that region to the semiconductor layers. Consequently, less current is wasted and better efficiency of applied current is obtained by the arrangements of the present invention as compared to a conventional device with the same amount of current being applied.
The arrangements of the present invention also improve the quality of the semiconductor device. By decreasing the current flow in the vicinity of mechanical damages that were made at the time of wire bonding, deterioration of the device can be inhibited. As a result, the product life span of the device is longer, or its quality is improved as a whole. This improvement may be observed by performing an accelerating deterioration exam.
Other objects, features, and characteristics of the present invention will become apparent upon consideration of the following description in the appended claims with reference to the accompanying drawings, all of which form a part of the specification, and wherein referenced numerals designate corresponding parts in the various FIGS.